NASA's James Webb Telescope has possibly detected the presence of a molecule that could signal life as we know it on a distant exoplanet.
Dimethyl sulfate (DMS) was possibly detected on K2-18b which lies 120 light years from Earth in the Leo constellation. On Earth, this is only produced by life, primarily by phytoplankton in marine environments.
The exoplanet lies within the habitable zone of its star and is 8.6 times the size of Earth.
Methane and carbon dioxide are abundant in the atmosphere, with a scarcity of ammonia supporting a hypothesis that K2-18b has a water ocean.
This adds to recent studies that the planet could be what's known as a Hycean exoplanet — one with the potential to possess a hydrogen-rich atmosphere and sustain a water ocean-covered surface.
Astronomer Nikku Madhusudhan said that the findings underscore the importance of considering diverse habitable environments in the search for life elsewhere.
"Traditionally, the search for life on exoplanets has focused primarily on smaller rocky planets, but the larger Hycean worlds are significantly more conducive to atmospheric observations.
"Upcoming Webb observations should be able to confirm if dimethyl sulfate is indeed present in the atmosphere of K2-18b at significant levels."
It is the first time that astronomers have detected the possibility of DMS in a planet orbiting a distant star.
However, K2-18b's position in the habitable zone and the detection of carbon-rich molecules in its atmosphere does not necessarily mean that the planet can support life.
The planet's interior likely contains a mantle of high-pressure ice, like Neptune, but with a thinner hydrogen atmosphere and an ocean surface which could be too hot to be habitable or be liquid.
Astrophysicist Subhajit Sarkar said that planets like this are the most common type known so far in the galaxy, characterised as a sub-Neptune due to its size being between that of Earth and Neptune.
"We have obtained the most detailed spectrum of a habitable-zone sub-Neptune to date, and this allowed us to work out the molecules that exist in its atmosphere."
The James Webb Space Telescope works by analysing the light passing through a planet's atmosphere which contains the chemical signature of molecules in its atmosphere. By splitting the light into its components and identifying gaps created by the chemical absorption of light in a planet's atmosphere, researchers can figure out its chemical composition.
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